One type of prior nonvolatile memory is flash erasable and electrically programmable read-only memory ("flash EPROM"). A prior flash EPROM can be programmed, and once programmed, the contents of the prior flash EPROM can be erased by electrical erasure. The prior flash EPROM may then be reprogrammed with new data.
One type of prior flash EPROM includes a volatile memory buffer within the memory chip. The internal volatile memory buffer is used to buffer data to be programmed into the prior flash EPROM. After buffering, the data is then written into the memory array of the prior flash EPROM. The buffer resides on the same substrate as the circuitry of the prior flash EPROM. As is known, a volatile memory is typically faster than a nonvolatile memory for the read and write operations. The use of the volatile memory buffer in the flash EPROM therefore increases the programming throughput of the flash EPROM by first buffering data in the volatile memory buffer. The volatile memory buffer also enables fast access to the buffered data by the write control circuit of the flash EPROM during of the programming data into the flash memory array.
Moreover, the volatile memory buffer can be a multiple page interleaved volatile memory buffer to achieve further increase in the programming throughput of the flash EPROM. The interleaved buffer allows one page of the buffer to be loaded with data while the data stored in another page of the buffer is programmed into the flash memory array.
Disadvantages are, however, associated with the prior flash EPROM that includes the on-chip volatile memory buffer. One disadvantage is that the buffered data stored in the volatile memory buffer is typically lost when the prior flash EPROM is disconnected from the power supply. Typically, when the entire volatile memory buffer or one page of the buffer is full of data, the write control circuit of the flash ERPOM then empties the buffer or the page of the buffer by programming the data into the memory array. When the buffer is not full or when the write control circuit is not requested to program the data stored in the buffer, the write control circuit does not program the data stored in the buffer into the memory array of the flash EPROM. If the power supply is then disconnected from the flash EPROM, the data buffered in the volatile memory buffer will be lost, which adversely affects data integrity of the flash EPROM.
It is known in the prior art that a computer system with a volatile memory device can include a backup power supply to power the volatile memory during a failure in the primary power supply. The volatile memory and the backup power supply are typically mounted within the computer system. When the computer system experiences a power loss, the volatile memory is connected to the backup power supply such that data can be retained in the volatile memory.